ABSTRACT
The variability of heart rate (HR) and arterial pressure (AP), and their responses to head-up tilt test (HUTT) was investigated in post-Covid-19 syndrome (PCS) patients, reporting tachycardia and/or postural hypotension. PCS patients were tachycardic and showed attenuation of the following parameters: RMSSD; power of RR spectra at HF; occurrence of 2UV pattern of RR (symbolic analysis); and sample entropy. Basal AP and LF power of systolic AP were similar between PCS patients and control subjects; while 0V patterns of AP were exacerbated in PCS patients. Despite tachycardia and decrease in RMSSD, no parameter changed during HUTT in PCS patients. PCS patients reassessed after 6 months showed higher HF power of RR spectra and higher percentage of 2UV pattern of RR. Moreover, the reassessed PCS patients showed a lower occurrence of 0V patterns of AP, while the HUTT elicited HR and AP responses identical to control subjects. The HR and AP variability suggest an autonomic dysfunction with sympathetic predominance in PCS patients; while the lack of responses of HR and BP variability indices during HUTT indicates a marked impairment of autonomic control. However, the reassessment of PCS patients showed that the noxious effect of the PCS tended to fade over time.